Combination process for producing LPG and aromatic rich material from naphtha

ABSTRACT

Processing of reformate product of catalytic reforming to produce significant yields of LPG and BTX as well as aromatic enriched reformate with a ZSM-5 type crystalline zeolite is described.

United States Patent Bonacci et a]. [45] Dec, 23, 1975 COMBINATIONPROCESS FOR 3,109,979 1/1973 Chu 423/328 PRODUCING LPG AND AROMATIC RICH3,729,409 4/1973 Chen............ 208/135 ER! 3,756,942 9/1973Cattanach.... 2081137 MAT FROM NAPHTHA 3,760,024 9/1973 Cattanach260/673 [75] inventors: John C. Bonacci, Cherry Hill; Henry 3,766,09310/1973 Chu 252/455 Z P. Ireland, Woodbury; Thomas 3,767,565 10/1973Chen 208/134 S i Ch Hi a f Ni 3,806,443 4/1974 Maziuk 208/60 3,832,4498/1974 Rosinski et al. ZOE/I X [73] Assignee: Mobil Oil Corporation, NewYork, 3,849,290 11/1974 Wise et a1. 208/66 NY. 3,856,873 12/1974 Burress260/668 A [22] Filed: 1975 Primary ExaminerDelbe1-t E. Gantz [2]] Appl.No: 538,221 Assistant Examiner-G. E. Schmitkons Attorney, Agent, orFirmC. A. Huggett; M. G.

Gilman [52] US. Cl. 208/80; 208/66; 208/79; 208/111; 208/120; 260/672 T51 1111. c1. C10G 37/06; B01J 29/28 [57] ABSTRACT [58] Field of Search208/80, 66, 79 flssing 0f reformate product of catalytrc reformmg toproduce significant yields of LPG and BTX as well [56] References Citedas aromatic enriched reformate with a ZSM-S type UNITED STATES PATENTScrystalline zeolite is described. 3,702,886 11/1972 Argauer et al423/328 20 Claims, 1 Drawing Figure C Reformale US. Patent Dec. 23, 19753,928,174

C Reformofe COMBINATION PROCESS FOR PRODUCING LPG AND AROMATIC RICHMATERIAL FROM NAPI'ITI-IA BACKGROUND OF THE INVENTION Reforming ofhydrocarbons is a widely used process in petroleum technology forupgrading hydrocarbon fractions such as naphthas, gasolines andkerosines to improve the antiknock characteristics thereof. Hydrocarbonfractions suitable for upgrading by reforming are composed of normal andbranched paraffins, naphthenic hydrocarbons and even some aromatichydrocarbons. During reforming a multitude of reactions take placeincluding dehydrogenation, isomerization, dehydrocyclization,hydrocracking, and combinations thereof to yield a product of increasedaromatics con tent and branched chain hydrocarbons. Thus in reforming itis desired to dehydrogenate the naphthenic hydrocarbons to producearomatics, cyclize straight chain paraffins to form naphthenes, toconvert C ring compounds to C ring compounds which are dehydrogenated toform aromatics, isomerize normal and branched paraffin hydrocarbons toyield higher octane branched chain hydrocarbons and effect a controlledhydrocracking of hydrocarbon constituents which are of undesired octanecharacteristics.

Normal and slightly branched paraffin hydrocarbons found in the abovehydrocarbon fractions are generally of low octane rating. Highlybranched-chain paraffin hydrocarbons, on the other hand, arecharacteristic of higher octane ratings. Therefore, one object ofreforming is to effect isomerimtion of the normal and slightly branchedchain paraftins to higher octane products by any one of theaforementioned reactions. The production of aromatics during reformingis accomplished by one or more of the above identified reactions leadingto the production of naphthenes which are then dehydrogenated toaromatics such as benzene, toluene and Xylene. One method for producingaromatics involves the isomerization of alkyl cyclopentanes to formcyclohexanes which thereafter are dehydrogenated to aromatics.

Ever since the concept of catalytic reforming was developed andcommercially adopted, the refiner has been concerned with improving uponthe selectivity of the product obtained and thus has strived to reduceyields of carbon and normally gaseous product materials since suchmaterials represent a loss in desired liquid product. Thus smallimprovement in product selectivity has been gained with difficulty sincethere is a limit to the quantity of normally liquid constituents ofdesired octane rating that can be produced from a given charge.Consequently increases in product selectivity are viewed withconsiderable interest particularly if the selectivity increases can beassociated with products of economic interest to the refiner. It hasbeen found that the selectivity of a particular product slate orcomposition can be considerably enhanced by following the concepts andsequence of steps Comprising this invention.

THE INVENTION This invention relates to a method and combination ofprocessing steps for effecting a selective conversion and arearrangement of petroleum hydrocarbon constituents to form aromaticenriched products and improve yields of LPG materials. In one aspect thepresent invention is concerned with one or more methods for selectivelyconducting chemical reactions with an arrangement of catalyticcompositions possessing selective reaction properties with respect todifferent hydrocarbon components existing in the naphtha boiling rangematerial. In yet another aspect the present invention relates toeffecting a selective catalytic conversion of hydrocarbon componentscomprising, normal and isoparaffin hydrocarbon components in a se quenceof hydrogenating conversion steps maintained under operating conditionsselected to obtain products rich in aromatics and LPG material. Morespecifically, the invention is concerned with an arrangement andsequence of catalytic reactions designed to manipulate the reaction ofhydrocracking, dehydrogenation, isomerization and dehydrocyclization toimprove upon the yields of LPG products and aromatic components readilyseparated by distillation.

The present invention is concerned with contacting a relatively wideboiling range naphtha hydrocarbon material boiling in the range of Chydrocarbons up to about 380 or 400F. under selective reformingconditions in the presence of a platinum type reforming catalyst. Inthis reforming operation the conditions employed lead to the productionof relatively low octane branched and normal paraffin compounds whichare available for conversion and production of additional LPG products.The reforming catalyst may be relied upon to hydrocrack these low octanecompounds formed during the reforming operation but it is preferred thatthe refonnate product comprising any C and higher boiling normalparafiin constituents be subjected to a selective zeolite hydrocrackingoperation designed to convert low boiling normal paraffins to LPGproduct. Thus the present invention includes the selective cracking oflow and high boiling normal paraffin components comprising the naphthaboiling material processed in the combination of catalytic contact stepscomprising this invention. It includes reforming a naphtha charge underreforming conditions providing normal and branched chain hydrocarbonscomponent along with reactions of dehydrogenation and dehydrocyclizationcomprising catalytic reforming. This relationship between normal andbranched chain hydrocarbon components provides normal paraffinconstituents suitable for conversion to LPG material.

A platinum type reforming catalyst including bimetallic andnon-bimetallic reforming catalysts and those comprising platinum orpalladium in combination with another Group VIII metal component such asrhenium, iridium, ruthenium and osmium promoted with a halogen willindiscriminately effect hydrocracking under elevated temperaturereforming conditions of the normal and branched paraffin componentscomprising the hydrocarbon material in the reforming operation. Thusemploying a platinum type reforming catalyst under controlledisomerizing and hydrocracking severity conditions may be relied upon toproduce LPG type products or products more easily converted to LPGproducts. That is, hydrocracking reactions performed with platinumreforming catalysts are more usually rate controlled reactions wherein,for example, a normal C, hydrocarbon will crack more easily than a Chydrocarbon or a lower carbon number paraffin and thus a high severityreforming operation would be required to crack, for example, a Cparaffin. However, such a high severity non-selective hydrocrackingoperation with the platinum reforming catalyst is undesirable sincecracking of branched C and C hydrocarbons will be accomplished beforecracking of normal hexane. This will result in cracking desired highoctane branched chain hydrocarbons. Furthermore, such an operationproduces an undesired mixture of light gases particularly comprising C,and C hydrocarbons rather than C and C hydrocarbons, On the other hand,using the small pore selective hydrocracking catalyst described herein,cracking the lower boiiing C and C paraffins more effectively for theproduction of LPG products. Thus by maintaining a selective balance inrate control and equilibrium controlled hydrocracking reactions with thedifferent catalysts described herein and particularly suitable for thispurpose, an improved overall yield of LPG products can be obtained alongwith an aromatic rich product by the present invention.

Crystalline aluminosilicate conversion catalysts identified with theprior art which are not selective within the limits defined herein orthose particularly known as methane producers rather than producers ofpropane and butane are of little interest in pursuing the concepts ofthis invention. Furthermore, high methane producing cyrstallinealuminosilicate catalysts generally small pore crystalline zeolitespromoted with Zn, Cd and Hg or other hydrocracking catalyst compositionswhich non selectively produce gaseous streams rich in methane are oflittle interest for practicing the concept of this invention unless theycan be controlled by operating conditions to exclude the undesirableproduction of light gaseous hydrocarbon constituents particularlymethane and ethane.

ln the interest of convenience to a better understand ing of theconcepts of the present invention the platinum type of reformingcatalyst used will be referred to as catalyst A hereinafter. and thedescribed selective crystalline aluminosilicate hydrocracking catalystrelied upon particularly for the production of LPG gases will bereferred to hereinafter as catalyst B.

The platinum type reforming catalyst, catalyst A, selected for use inthe sequence of process steps of this invention may be selected from anyone of a number of known prior art reforming catalysts suitable foraccomplishing the results desired. These catalysts include generally.for example, alumina as the carrier material for one or morehydrogenation-dehydrogenation components distributed thereon with thealumina being in either the eta, chi, gamma or mixed forms thereof. Thealumina carrier is promoted with. for example, one or more Group Vlllmetal components either with or without an acidic promoter such assilica, boron or a halogen. The platinum type of reforming catalyst isintended to include platinum. palladium, osmium, iridium, ruthenium,rhenium and mixtures thereof deposited on an alumina containing carrieror support with the alumina components generally being in an amount upto about 95% by weight. Other components such as magnesium. zirconium,thorium, vanadium and titanium may also be combined or distributed inthe alumina carrier. The platinum type catalyst may also include variousamounts of halogen such as chlorine or fluorine in amounts ranging fromabout 0.1 up to about 10%, usually not more than 5 or 6%. The platinumreforming catalysts described may be one of those described in the priorart as homogeneous mixtures of metal components, alloys. and metalhalide complexes thereof. A bimetal catalyst composition suitable forthe reforming operation of this invention may be platinum combined witheither rhenium, ruthenium, osmium or 4 iridium and an alumina carrierpromoted with chlorine to provide desired acid activity.

ln reforming operations it is known that as the reforming severity isincreased to achieve higher and higher product octane number, the octanenumber increase is obtained primarily by way of paraffin aromatizationand 5 carbon ring aromatization. At the relative high severityconditions required for paraffin to aromatic dehydrocyclizationreactions to become im portant, these are accompanied by progressive andnon-selective elimination by hydrocracking of remaining paraffins tolight gaseous products thus increasing octane number at the expense ofsubstantial liquid volume loss. It is, therefore, preferred toselectively control the reforming operation severity to restrict thechemical reactions encountered therein to minimize the production of lowoctane liquid and undesired gaseous component in favor of producingbranched chain hydrocarbons in an aromatic enriched product ofrelatively high octane rating. Accordingly, the method and combinationof process steps herein described provide significant and unusualbenefits by adjusting the reaction mechanisms to implement and improvethe production of LPG products as well as high octane aromatic productswithout unusual sacrifice of yield of liquid products.

The operating conditions employed in the process combination of thisinvention and particularly those of the reforming operation with type Acatalysts are those conditions which promote dehydrogenation ofnaphthenes along with reactions associated with paraffin isomerizationwhich establish a relationship between normal paraffins to branchedparaffins and include operating temperatures selected from the range ofabout 800F to about 1000F and preferably from 850F up to about 980F.,liquid hourly space velocity in the range of about 0.1 to about 10,preferably about 0.5 to about 5; a pressure in the range of aboutatmospheric up to about 600 p.s.i.g. and preferably about to about 400p.s.i.g. and a hydrogen to hydrocarbon ratio of about 0.5 to about 20and preferably about I to 10.

The type B catalysts referred to herein are members of a special classof zeolites exhibiting some unusual properties. These zeolites induceprofound transforma tions of aliphatic hydrocarbons to aromatichydrocarbons in commercially desirable yields and are generally highlyeffective in alkylation. isomerization, disproportionation and otherconversion reactions involving aromatic hydrocarbons. Although they haveunusually low alumina contents, i.e., high silica to alumina ratios,they are very active even with silica to alumina ratios exceeding 30.This activity is surprising since catalytic activity of zeolites isgenerally attributed to framework aluminum atoms and cations associatedwith these aluminum atoms. These zeolites retain their crystallinity forlong periods in spite of the presence of steam even at high temperatureswhich induce irreversible collapse of the crystal framework of otherzeolites, e.g., of the X and A type. Furthermore, carbonaceous deposits.when formed, may be removed by burning at higher than usual temperaturesto restore activity. In many environments the zeolites of this classexhibit very low coke forming capability, conducive to very long timeson stream between burning regenerations.

An important characteristic of the crystal structure of this class ofzeolites is that it provides constrained access to, and egress from, theintra-crystalline free space by virtue of having a pore dimensiongreater than about 5 Angstroms and pore windows of about a size such aswould be provided by lO-membered rings of oxygen atoms. lt is to beunderstood, of course, that these rings are those formed by the regulardisposition of the tetrahedra making up the anionic framework of thecrystalline aluminosilicate, the oxygen atoms themselves being bonded tothe silicon or aluminum atoms at the centers of the tetrahedra. Briefly,the preferred zeolites useful in type B catalysts in this inventionpossess, in combination: a silica to alumina ratio of at least about 12;and a structure providing constrained access to the crystalline freespace.

The silica to alumina ratio referred to may be determined byconventional analysis. This ratio is meant to represent, as closely aspossible, the ratio in the rigid anionic framework of the zeolitecrystal and to exclude aluminum in the binder or in cationic or otherform within the channels. Although zeolites with a silica to aluminaratio of at least 12 are useful, it is preferred to use zeolites havinghigher ratios of at least about 30. Such zeolites, after activation,acquire an intracrystalline sorption capacity for normal hexane which isgreater than that for water, i.e., they exhibit hydrophobic" properties.It is believed that this hydrophobic character is advantageous in thepresent invention.

The zeolites useful as B catalysts in this invention freely sorb normalhexane and have a pore dimension greater than about 5 Angstroms. Inaddition, their structure must provide constrained access to some largermolecules. It is sometimes possible tojudge from a known crystalstructure whether such constrained access exists. For example, if theonly pore windows in a crystal are formed by S-membered rings of oxygenatoms, then access by molecules of larger cross-section than normalhexane is substantially excluded and the zeolite is not of the desiredtype. Zeolites with windows of l0membered rings are preferred, althoughexcessive puckering or pore blockage may render these zeolitessubstantially ineffective. Zeolites with windows of lZ-membered rings donot generally appear to offer sufficient constraint to produce theadvantageous conversions desired in the instant invention, althoughstructures can be conceived, due to pore blockage or other cause, thatmay be operative.

Rather than attempt to judge from crystal structure whether or not azeolite possesses the necessary constrained access, a simpledetermination of the constraint index may be made by continuouslypassing a mixture of equal weight of normal hexane and 3methylpentaneover a small sample, approximately 1 gram or less, of zeolite atatmospheric pressure according to the following procedure. A sample ofthe zeolite, in the form of pellets or extrudate, is crushed to aparticle size about that of coarse sand and mounted in a glass tube.Prior to testing, the zeolite is treated with a stream of air at lO0OFfor at least 15 minutes. The zeolite is then flushed with helium and thetemperature adjusted between 550F and 950F to give an overall conversionbetween l0% and 60%. The mixture of hydrocarbons is passed at l liquidhourly space velocity (i.e., 1 volume of liquid hydrocarbon per volumeof catalyst per hour) over the zeolite with a helium dilution to give ahelium to total hydrocarbon mole ratio of 4:1. After minutes on stream,a sample of the effluent is taken and analyzed, most conveniently by gaschromatography, to determine the fraction remaining unchanged for eachof the two hydrocarbons.

The constraint index" is calculated as follows:

logflfraction of n-hcxane remaining) C(mslralm Index 7: l i fraction oflmethylpentanc remaining) CAS TMA Offrctitc ZSM- l 2 Beta H-Zeolon REYAmorphous Silica-alumina Erionitc The class of Zeolites defined hereinis exemplified by ZSM-S, ZSM-ll, ZSM-lIZ, ZSM-2l and other similarmaterials. Recently issued US. Pat. No. 3,702,886 describing andclaiming ZSM-S is incorporated herein by reference.

ZSM-ll is more particularly described in US. Pat. No. 3,709,979, theentire contents of which are incorporated herein by reference.

ZSM-l2 is more particularly described in US. Pat. No. 3,832,449, theentire contents of which are incorporated herein by reference.

US. application, Ser. No. 358,192, filed May 7. 1973, now abandoned, theentire contents of which are incorporated herein by reference, describesa zeolite composition, and a method of making such, designated as ZSM-2lwhich is useful in this invention. Recent evidence has been adducedwhich suggests that this composition may be composed of two differentzeolites, one or both of which are the effective material insofar as thecatalyst for this invention is concerned.

The specific zeolites described, when prepared in the presence oforganic cations, are substantially catalytically inactive, possiblybecause the intracrystalline free space is occupied by organic cationsfrom the forming solution. They may be activated by heating in an inertatmosphere at lO0OF for 1 hour, for example. followed by base exchangewith ammonium salts followed by calcination at lO0OF in air. Thepresence of organic cations in the forming solution may not beabsolutely essential to the formation of this special type zeolite;however, the presence of these cations does appear to favor theformation of this special type of zeolite. More generally, it isdesirable to activate this type zeolite by base exchange with ammoniumsalts followed by calcination in air at about lO0OF for from about 15minutes to about 24 hours.

Natural zeolites may sometimes be converted to this type zeolite byvarious activation procedures and other treatments such as baseexchange, steaming, alumina extraction and calcination, alone or incombinations. Natural minerals which may be so treated includeferrierite, brewsterite, stilbite, dachiardite, epistilbite, heu

7 landite and clinoptilolite. The preferred crystalline aluminosilicatesare ZSM-S, ZSM-l l, ZSM-l2 and ZSM-Zl, with ZSM-5 particularlypreferred.

The zeolites used as catalysts in this invention may be in the hydrogenform or they may be base exchanged or impregnated to contain ammonium ora metal cation complement. It is desirable to calcine the Zeolite afterbase exchange. The metal cations that may be present include any of thecations of the metals of Groups 1 through VIII of the periodic table.However, in the case of Group IA metals, the cation content should in nocase be so large as to substantially eliminate the activity of theZeolite for the catalysis being employed in the instant invention. Forexample, a completely sodium exchanged H-ZSM-S appears to be largelyinactive for shape selective conversions required in the presentinvention.

In a preferred aspect of this invention, the zeolites useful ascatalysts herein are selected as those having a crystal frameworkdensity, in the dry hydrogen form, of not substantially below about 1.6grams per cubic centimeter. It has been found that zeolites whichsatisfy all three of these criteria are most desired. Therefore, thepreferred catalysts of this invention are those using zeolites having aconstraint index as defined above of about 1 to 12, a silica to aluminaratio of at least about 12 and a dried crystal density of notsubstantially less than about 1.6 grams per cubic centimeter. The drydensity for known structures may be calculated from the number ofsilicon plus aluminum atoms per 1000 cubic Angstroms, as given, e.g., onpage 19 of the article on Zeolite Structure by W. M. Meier. This paper,the entire contents of which are incorporated herein by reference, isincluded in Proceedings of the Conference on Molecular Sieves, London,April 1967," published by the Society of Chemical lndustry, London,1968. When the crystal structure is unknown, the crys tal frameworkdensity may be determined by classical pyknometer techniques. Forexample, it may be determined by immersing the dry hydrogen form of thezeolite in an organic solvent which is not sorbed by the crystal. It ispossible that the unusual sustained activity and stability of this classof zeolites is associated with its high crystal anionic frameworkdensity of not less than about 1.6 grams per cubic centimeter. This highdensity of course must be associated with a relatively small amount offree space within the crystal, which might be expected to result in morestable structures. This free space, however, seems to be important asthe locus of catalytic activity.

Crystal framework densities of some typical zeolites including somewhich are not within the preview of this invention are:

-continued Void Framework Zeolite Volume Density The heavier reformatefraction is overwhelmingly aromatic in composition, the aromaticscomprising at least about volume percent, preferably at least aboutvolume percent, thereof. At least a portion, and preferably all, of thisheavier reformate is con tacted with a distinct mass of type B catalystunder conditions conducive to substantially eliminating any aliphaticcomponents thereof. These conditions also induce aromatic isomerization,disproportionation, alkylation, dealkylation, transalkylation and sidechain splitting so as to produce a product which is substan tiallybenzene and methyl substituted benzenes up to about C BTX preferablypredominates in this product.

The light reformate comprises substantial proportions of aliphatic aswell as aromatic components. It is contacted with a separate anddistinct mass of type B catalyst under conditions conducive to crackingout the lower octane aliphatic components to produce LPG components andto simultaneously increase the propor tion of aromatics at leastpartially by alkylation of existing aromatics with fragments produced bysuch cracking.

The two separate and distinct type B catalyst conversions may be carriedout under substantially similar or widely different reaction conditionsdepending upon the exact compositions of the light and heavier reformatefractions and upon the desired product distribution. It has been found,however, that if the reformate is split in the manner set forthhereinabove, each of the type B catalyst conversion performs itsintended function admirably whereas if the reformate is splitdifferently, these conversion are substantially less efficient atproducing the desired product slate of high quality, aromatic enrichedgasoline, high quality substantially aliphatic free aromaticsconcentrate, and large quanti ties of LPG.

The operating conditions selected for processing the light reformatefraction boiling below about 240F particularly include an operatingpressure within the range of 200 to 1000 psig; a temperature within therange of about 500F to 800F; a volume hourly space velocity in the rangeof about 1 to 4 and a hydrogen to hydrocarbon ratio within the range ofabout 1 to 10 to 1. Hydrogen consumption is about or more SCF/Bdepending on the charge composition and operating conditions selected.Processing the heavy reformate fraction is preferably accomplished undermore severe operating conditions including a temperature within therange of about 750 to 900F; a space velocity (vol. basis) in the rangeof about 0.5 to 2; a hydrogen to hydrocarbon ratio in the range of1-20/1 and a pres sure within the range of about 200 to 1000 psig.Hydrogen consumption for the more severe operation is within the rangeof 2004400 SCF/B.

BRIEF DESCRIPTlON OF THE DRAWING The drawing is diagrammatic sketch inelevation of the process combination comprising the separation ofreformate product of catalytic reforming into a light and heavyreformate product fractions which are thereafter separately processedover type B catalyst under lower and higher severity conditions asaforesaid to particularly produce LPG, high octane gasoline and abenzene-toluene-xylene rich fraction.

Referring now to the drawing, by way of example, a C9 full boiling rangeproduct of naphtha reforming is charged to the process by conduit 2. Thenaphtha feed to a catalytic reforming operation may be one boiling inthe range of C hydrocarbon up to about 380 or 400F. Reforming of naphthaboiling range hydrocarbons is well known in the prior art as discussedabove and is a part of this invention to the extent that the materialprocessed is a reformate product of catalytic reforming comprising a C;reformate. The reformate charge introduced by conduit 2 to stabilizer 4is separated in the stabilizer to recover toluene enriched C reformatematerial from the bottom thereof by conduit 8. C and lower boilingcomponents are recovered from the top of the stabilizer by conduit 10and then passed to gas recovery equipment not shown to separate LPGmaterials from other gasiform materials.

A portion of the material withdrawn by conduit 8 from the bottom of thestabilizer is passed to gasoline pool equipment. The remaining portionof the (3,;* material is passed by conduit 12 to a second separationzone 14, hereinafter sometimes referred to as a reformate splitter. Inseparation zone 14, conditions are maintained to separate the Creformate into an overhead fraction comprising some toluene andprimarily lower boiling components withdrawn therefrom by conduit 16. ACf toluene-xylene rich fraction is withdrawn from the bottom portion ofseparation zone 14 by conduit 18. Separation of the CJ reformate in zone14 is accomplished to provide a cut point between the fractions withinthe range of about 200 to about 240F.

The overhead fraction comprising primarily C and lower boilingcomponents withdrawn by conduit 16 is passed with added hydrogen to acatalyst zone 20 containing a ZSM-S type of crystalline zeoliteconversion catalyst. In zone 20, the fraction comprising toluene andlower boiling components is subjected to processing conditionscomprising a pressure of about 400 psig at a start of run temperature ofabout 550F. The reactant material is passed in contact with the catalystat a volume hourly space velocity of about 2 and a hydrogen tohydrocarbon ratio of at least 1/ 1. In zone 20 the light reformatecomprising aromatic and C minus saturated hydrocarbons are processed toparticularly produce LPG materials comprising propane and butane andsome alkyl aromatics comprising toluene. The product effluent of zone 20is then passed by conduit 22 to a high pressure separation zone 24. Inhigh pressure separator 24, a separation is made which permits therecovery of C and lower boiling material comprising hydrogen from anupper portion of the zone by conduit 26. Some of this material may bewithdrawn by conduit 28 and used as fuel. The remaining portion of thematerial in conduit 26 is combined with makeup hydrogen added by conduit30, compressed in compressor 32 to raise the pressure of this recyclestream about 50 pounds before recycle by conduit 34 to zone 20.

A product material comprising C and higher boiling components includingbenzene and toluene separated in zone 24 is withdrawn essentially as aliquid stream from the lower portion of separation zone 24 by conduit 36and passed in its entirety to separation zone 4 10 wherein the C andlower boiling components are removed as overhead material and processedas above briefly discussed.

The heavy Cf reformate material, enriched with C? components from theseparator 24, withdrawn from the lower portion of separation zone 14 isa toluene-xylene rich stream comprising Cf paraffins, having at mostabout 0.1 weight percent C parafl'ms, and boiling above about 225F whichmixture is passed in a desired amount by conduit 38 to a second ZSM-5zeolite catalytic conversion zone 40. A portion of this toluene xyleneenriched reformate in conduit 18 may be withdrawn as a product streamfor use as desired. In zone 40, the herein identified Cf reformate isprocessed in the presence of added hydrogen which may come from conduit28 over a ZSM-S type zeolite under relatively more severe processingconditions designed to particularly crack paraffin components andconvert the aromatic containing reformate to a light aromatics mixturecomprising (BTX) benzene, toluene and xylene by a combination ofdealkylation and disproportionation reactions. In this catalyticconversion operation it is proposed to employ an operating pressure ofabout 401) psig and a start of run temperature of about 750F. A hydrogento hydrocarbon ratio of about 4/1 is used with a reactant volume spacevelocity of about 1. It is particularly important that the processingconditions of zone 40 be selected to particularly crack the paraffins tolower boiling components comprising LPG products and disproportionatecharged aromatics to form a mixture of benzene, toluene, and aromaticssince these materials are of a boiling range easily separated by simpledistillation.

The product effluent of the aromatic forming zone 40 is passed byconduit 42 to a high pressure separation zone 44. In separation zone 44a hydrogen rich gaseous stream is separated and recycled by conduit 46to conduit 38 communicating with zone 40. Hydrogen rich make up gas isadded to the recycled gas by conduit 48. The remaining product separatedin zone 44 comprising light aromatics and lower boiling components ofcracking are passed by conduit 50 to a separation zone 52 maintained ata pressure of about psig and a temperature of about 450F. In separationzone 52 a separation is made between light aromatics comprising benzeneand higher boiling aromatics and reaction components boiling below aboutbenzene. Thus a light aromatic rich fraction is withdrawn by conduit 54from zone 52 for further processing by distillation and other means notshown into desired components.

Materials generally lower boiling than benzene and comprising hexane andlower boiling components is withdrawn from separator 52 by conduit 56for recycle to stabilizer 4 as by conduit 36.

An important aspect of this invention resides in flashing the product ofshape selective conversion of light reformate, preferably in a highpressure separator. to split it into a gas and a higher octane gasolineliquid. The liquid is recycled to the stabilizer along with the fullrange reformate. Thus the heavier reformate from the splitter isenriched with C components (predominantly Cf alkyl benzenes) from thishigher octane gasoline liquid product.

It is most important that a portion of the toluene enriched C reformatematerial from the stabilizer be drawn down out of the system. Thisproduct is excellent gasoline.

Having thus generally described the invention and presented a specificexample in support thereof, it is to be understood that no unduerestrictions are to be imposed by reason thereof except as defined bythe following claims.

We claim:

1. A method for redistributing the paraffin-aromatic components of areformate product of catalytic reforming comprising C and higher boilinghydrocarbons which comprises,

separating C and lower boiling components of catalytic reforming from Cand higher boiling materials in a first separation zone, separating theC and higher boiling material in a second separation zone into a firstfraction comprising some C components and lower boiling parafi'in andaromatic components and a second fraction comprising C and higherboiling parafi'ins and aromatic components, passing said first fractionin contact with a first crystalline zeolite catalyst having propertiesfor cracking paratfins to form LPG materials and redistribute the ratiobetween benzene and toluene components in the feed, separating productmaterial of said first crystalline zeolite conversion operation intogaseous material comprising C and lower boiling material from materialcomprising C and higher boiling components, passing the C and higherboiling material to said first separation zone,

passing a portion of said second fraction comprising C and higherboiling paraffins and aromatics in contact with a separate second massof crystalline zeolite catalyst having properties for cracking saidparafiins and disproportionating aromatic to form a mixture of benzene,toluene and xylene; separating the product of said second zeolitecatalyst conversion operation to recover a hydrogen rich stream, astream rich in benzene, toluene and xylene aromatics and an intermediateproduct stream lower boiling than said aromatic rich stream, andrecycling said intermediate product stream to said first separationzone.

2. The method of claim 1 wherein hydrogen rich gas is passed to eachzeolite catalyst conversion zone.

3. The method of claim 1 wherein a C reformate fraction enriched intoluene is withdrawn from said first separation zone.

4. The method of claim 1 wherein a toluene-xylene rich fraction iswithdrawn from said second separation zone.

5. The method of claim 1 wherein a hydrogen rich gas is separated fromthe product of each zeolite catalyst conversion operation and isrecycled to the catalyst operation.

6. The method of claim 1 wherein LPG product material of the processcombination is concentrated in the overhead product withdrawn from thefirst separation zone.

7. The method of claim 1 wherein the temperatures relied upon in thefirst zeolite catalyst conversion zone are within the range of 500F. to800F.

8. The method of claim 1 wherein the temperatures and operatingconditions relied upon in the other zeo lite catalyst conversion zoneare more severe than those used in the first catalyst conversionoperation.

9. The method of claim 1 wherein the formation of a benzene, toluene,xylene rich mixture is particularly promoted by the operating conditionsrelied upon in the second zeolite catalyst operation.

10. The method of claim 1 wherein the zeolite cata lyst is preferably aZSM-S type crystalline zeolite.

ll. A process of upgrading petroleum reformate to an aromaticsconcentrate comprising benzene, toluene and xylene (BTX), liquifiablepetroleum gas (LPG) comprising C and C components, and high octanegasoline comprising:

splitting at least a C,,* portion of said reformate into C? and Cfractions having minimum and maximum boiling points respectively ofabout 200 to 240F',

contacting said C? fraction with a crystalline aluminosilicate zeolitehaving a silica to alumina ratio of at least l2 and a constraint indexof l to 12 in a first conversion zone;

converting said C fraction in said first conversion zone at at leastabout 500F. to a product comprising C gas and a substantially aromaticliquid con centrate; contacting said C fraction with a crystalline aluminosilicate zeolite, having the ability to crack substantially onlyparaffinic components of said C fraction to Cf gas, in a secondconversion zone;

converting said C fraction in said second conversion zone at at leastabout 700F. to a product comprising C gas and an aromatics enrichedliquid product; and

recovering LPG from said Cf gas, said aromatics concentrate, and highoctane gasoline comprising said aromatics enriched liquid.

12. A process as claimed in claim 11 including admixing a portion ofsaid aromatics concentrate with said reformate prior to said splittingv13. A process as claimed in claim 11 including deleting a C fractionfrom said reformate and splitting the remaining CJ fraction.

14. A process as claimed in claim 11 including separating C and Ccomponents from said C gas.

15. A process as claimed in claim 11 including splitting a portion ofthe CJ portion of said reformate.

16. A process as claimed in claim 11, including admixing said aromaticsenriched liquid with said reformate prior to said splitting.

17. A process as claimed in claim 11 including admixing said aromaticsenriched liquid, a portion of said aromatics concentrate and saidreformate; and splitting said admixture into said Cf and C fractions.

18, A process as claimed in claim 11 including utilizing the samezeolite respectively in both of said conversions,

19. A process as claimed in claim 18 wherein said zeolite is a ZSM5.

20. A process as claimed in claim 11 wherein said C conversion iscarried out at about 500 to 800F,, about 200 to 1000 psig, about 1 to 4LHSV and about 2 to 10 to 1 hydrogen to hydrocarbon ratio; and whereinsaid C? conversion is carried out at about 750 to 900F., about 200 tol000 psig, about 0.5 to 2 LHSV and about 3 to 20 to 1 hydrogen tohydrocarbon ratio.

UNITED sTATEs PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3 ,928 ,17 r

DATED December 23, 1975 lNV ENTOR(S) John C. Bonacci, Henry R.

Thomas R. Stein It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Ireland and The Inventor's name Henry "P." Ireland should be Henry R.Ireland.

Signed and Scaled this RUTH C. MASON C. MARSHALL DANN Arresting Officer(mnmr'ssimwr njlarr rrs and Trademarks

1. A METHOD FOR REDISTRIBUTING THE PARAFFIN-AROMATIC COMPONENTS OF AREFORMATE PRODUCT OF CATALYTIC REFORMING COMPRISING C5 AND HIGHERBOILING HYDROCARBONS WHICH COMPRISES, SEPARATING C5 AND LOWER BOILINGCOMPONENTS OF CATALYTIC REFORMING FROM C6 AND HIGHER BOILING MATERIALSIN A FIRST SEPARATION ZONE, SEPARATING THE C6 AND HIGHER BOILINGMATERIAL IN A SECOND SEPARATION ZONE INTO A FIRST FRACTION COMPRISINGSOME C7 COMPONENTS AND LOWER BOILING PARAFFIN AND AROMATIC COMPONENTSAND A SECOND FRACTION COMPRISING C7 AND HIGHER BOILING PARAFFINS ANDAROMATIC COMPONENTS, PASSING SAID FIRST FRACTION IN CONTACT WITH A FIRSTCRYSTALLINE ZEOLITE CATALYST HAVING PROPERTIES FOR CRACKING PARAFFINS TOFORM LPG MATERIALS AND REDISTRIBUTE THE RATIO BETWEEN BENZENE ANDTOLUENE COMPONENTS IN THE FEED, SEPARATING PRODUCT MATERIAL OF SAIDFIRST CRYSTALLINE ZEOLITE CONVERSION OPERATION INTO GASEOUS MATERIALCOMPRISING C2 AND LOWER BOILING MATERIAL FROM MATERIAL COMPRISING C3 ANDHIGHER BOILING COMPONENTS, PASSING THE C3 AND HIGHER BOILING MATERIAL TOSAID FIRST SEPARATION ZONE, PASSING A PORTION OF SAID SECOND FRACTIONCOMPRISING C7 AND HIGHER BOILING PARAFFINS AND AROMATICS IN CONTACT WITHA SEPARATE SECOND MASS OF CRYSTALLINE ZEOLITE CATALYST HAVING PROPERTIESFOR CRACKING SAID PARAFFINS AND DISPROPORTIONATING AROMATIC TO FORM AMIXTURE OF BENZENE, TOLUENE AND XYLENE; SEPARATING THE PRODUCT OF SAIDSECOND ZEOLITE CATALYST CONVERSION OPERATION TO RECOVER A HYROGEN RICHSTREAM, A STREAM RICH IN BENZENE, TOLUNE AND XYLENE AROMATICS AND ANINTERMEDIATE PRODUCT STREAM LOWER BOILING THAN SAID AROMATIC RICHSTREAM, AND RECYCLIN SAID INTERMEDIATE PRODUCT STREAM TO SAID FIRSTSEPARATION ZONE.
 2. The method of claim 1 wherein hydrogen rich gas ispassed to each zeolite catalyst conversion zone.
 3. The method of claim1 wherein a C6 reformate fraction enriched in toluene is withdrawn fromsaid first separation zone.
 4. The method of claim 1 wherein atoluene-xylene rich fraction is withdrawn from said second separationzone.
 5. The method of claim 1 wherein a hydrogen rich gas is separatedfrom the product of each zeolite catalyst conversion operation and isrecycled to the catalyst operation.
 6. The method of claim 1 wherein LPGproduct material of the process combination is concentrated in theoverhead product withdrawn from the first separation zone.
 7. The methodof claim 1 wherein the temperatures relied upon in the first zeolitecatalyst conversion zone are within the range of 500*F. to 800*F.
 8. Themethod of claim 1 wherein the temperatures and operating conditionsrelied upon in the other zeolite catalyst conversion zone are moresevere than those used in the first catalyst conversion operation. 9.The method of claim 1 wherein the formation of a benzene, toluene,xylene rich mixture is particularly promoted by the operating conditionsrelied upon in the second zeolite catalyst operation.
 10. The method ofclaim 1 wherein the zeolite catalyst is preferably a ZSM-5 typecrystalline zeolite.
 11. A process of upgrading petroleum reformate toan aromatics concentrate comprising benzene, toluene and xylene (BTX),liquifiable petroleum gas (LPG) comprising C3 and C4 components, andhigh octane gasoline comprising: splitting at least a C6 portion of saidreformaTe into C7 and C7 fractions having minimum and maximum boilingpoints respectively of about 200* to 240*F; contacting said C7 fractionwith a crystalline aluminosilicate zeolite having a silica to aluminaratio of at least 12 and a constraint index of 1 to 12 in a firstconversion zone; converting said C7 fraction in said first conversionzone at at least about 500*F. to a product comprising C4 gas and asubstantially aromatic liquid concentrate; contacting said C7 fractionwith a crystalline aluminosilicate zeolite, having the ability to cracksubstantially only paraffinic components of said C7 fraction to C4 gas,in a second conversion zone; converting said C7 fraction in said secondconversion zone at at least about 700*F. to a product comprising C4 gasand an aromatics enriched liquid product; and recovering LPG from saidC4 gas, said aromatics concentrate, and high octane gasoline comprisingsaid aromatics enriched liquid.
 12. A process as claimed in claim 11including admixing a portion of said aromatics concentrate with saidreformate prior to said splitting.
 13. A process as claimed in claim 11including deleting a C5 fraction from said reformate and splitting theremaining C6 fraction.
 14. A process as claimed in claim 11 includingseparating C3 and C4 components from said C4 gas.
 15. A process asclaimed in claim 11 including splitting a portion of the C6 portion ofsaid reformate.
 16. A process as claimed in claim 11, including admixingsaid aromatics enriched liquid with said reformate prior to saidsplitting.
 17. A process as claimed in claim 11 including admixing saidaromatics enriched liquid, a portion of said aromatics concentrate andsaid reformate; and splitting said admixture into said C7 and C7fractions.
 18. A process as claimed in claim 11 including utilizing thesame zeolite respectively in both of said conversions.
 19. A process asclaimed in claim 18 wherein said zeolite is a ZSM-5.
 20. A process asclaimed in claim 11 wherein said C7 conversion is carried out at about500* to 800*F., about 200 to 1000 psig, about 1 to 4 LHSV and about 2 to10 to 1 hydrogen to hydrocarbon ratio; and wherein said C7 conversion iscarried out at about 750* to 900*F., about 200 to 1000 psig, about 0.5to 2 LHSV and about 3 to 20 to 1 hydrogen to hydrocarbon ratio.